1. Field of the Invention
The present invention relates to a technology to control switching of a circuit breaker, and more particularly to a switching controller for circuit breaker of which switching can be controlled, without increasing cost and installation space, even if the circuit breaker is in a lower branch system.
2. Description of the Related Art
In a device for controlling switching of a power circuit breaker, a method for controlling the opening/closing timing of the circuit breaker, so as not to generate transient phenomena in a system and power apparatus, has been proposed (e.g. see Patent Document 1). In the power switching controller according to prior art disclosed in Patent Document 1, the object is to prevent the generation of transient phenomena, which negatively influences the system and apparatus, under any switching conditions of the circuit breaker.
In addition to this prior art, a device for controlling the opening timing of the circuit breaker, so that the circuit breaker contact can have sufficient opening length when current is interrupted, has been proposed in order to avoid generating transient phenomena. A device for controlling the closing timing of the contact of the circuit breaker, in particular for controlling the closing timing according to the type of load, has also been proposed.
Such a switching controller for circuit breaker has a function to delay the output timing of an opening command signal or a closing command signal to the circuit breaker, to open or close the circuit breaker in a desired phase when the opening command signal or closing command signal has been detected. Because of this function, many switching controllers for circuit breaker, for not generating transient phenomena in the system or power apparatus, are now frequently used in actual power stations (e.g. see Non-Patent Document 1). This kind of switching control for a circuit breaker is called “synchronous opening control” or “synchronous closing control”.    Patent Document 1: Japanese Patent Application Laid-Open No. H3-156820    Non-Patent Document 1: Catalogue Publication 1HSM 9543 22-01en, Controlled Switching Buyer's Guide, Edition 1, 2004-05, ABB Power Technologies
In the case of prior art shown in Patent Document 1 and Non-Patent Document 1, one switching controller for circuit breaker must be used for one circuit breaker (one circuit breaker in this description refers to a circuit breaker for 3 phases, and hereafter in a case of using a single-phase operation-type circuit breaker, a 3-phase-1-set circuit breaker is regarded as one circuit breaker).
In a case of using the switching controller for a circuit breaker in a trunk power system, such as a 500 kV system, the ratio of the cost of the switching controller for circuit breaker is generally small compared with the cost of the circuit breaker itself. Therefore, in terms of cost, using one switching controller for one circuit breaker, like the case of the prior art, is not a major problem.
However if the switching controller for circuit breaker is used for a circuit breaker in a lower branch system, such as a power distribution system, using one switching controller for one circuit breaker, often causes a cost problem. Also in a power station in a lower branch system, such as a power distribution system, the installation space for a circuit breaker is often limited, so installing switching controllers of the same number as that of the circuit breakers is difficult.
In terms of maintenance of the switching controller for circuit breaker, a switching controller for circuit breaker used for many electric stations has a connection unit with such external equipment as a personal computer, and has a function to acquire various data when the switching of the circuit breaker has been controlled, including main circuit current waveforms and system voltage waveforms. Here, in order to connect the synchronous switching controller for the circuit breaker with such external equipment as a personal computer in the switching controller for circuit breaker, so as to acquire various data, normally dedicated communication software and maintenance software must be installed in the personal computer.
In the case of the switching controller for circuit breaker according to Non-Patent Document 1, for example, dedicated communication software and maintenance software are provided to the user on a CD-ROM, and the user must install the dedicated software in the personal computer using this CD-ROM. As a result of using this prior art, a personal computer in which the dedicated software is not installed cannot be connected to the switching controller for circuit breaker, which is very inconvenient to use in terms of storage and management of various acquired data.
Also in the case of the switching controller for circuit breaker according to Non-Patent Document 1, an RS-232C interface is used to connect with the personal computer, which is based on the local connection at the work site, and is inconvenient for remote control. If remote control is required, a modem must be connected to the personal computer so as to be connected with the switching controller for circuit breaker via a telephone line, which is not only inconvenient to use but also communication speed is slow and operation is inefficient.
Another problem is that only one switching controller for circuit breaker can be connected to one personal computer, which means that in order to perform maintenance and acquire various data for switching controllers for circuit breaker installed in a plurality of circuits, a connection switching operation is generated, and the operation efficiency deteriorates.